Before you start panicking over anything you read online, stop and consider the source. The Internet is full of misinformation, so the best thing to do is visit the sites of reputable organizations like the American Academy of Pediatrics or the Centers for Disease Control and Prevention for reliable, science-backed information, and share any concerns with your pediatrician. Be especially wary of anything you read on parent group Web sites, message boards, or blogs.
Although vaccination is one of the safest medical procedures around, the CDC and the FDA are constantly monitoring the effectiveness and safety of vaccines, and manufacturers are always trying to improve them. The vaccines currently used today are exceptionally safe. For example, only one in a million children who receives the MMR vaccine develops serious complications like encephalitis, an inflammation of the brain. On the other hand, if they contracted the measles, about one in 1,000 children would develop encephalitis and one in 3,000 would die from the disease. So it's clearly better to vaccinate.
We know it's hard to ignore all the online banter about the safety of vaccines, especially those discussions on the alleged connection between vaccines, mercury, and autism. Although it's natural to be concerned, it should set your mind at ease to know that study after study has shown no link between vaccines and the onset of autism or the rise of autism rates. In addition, in 2001 the FDA required that manufactures remove thimerosal (a mercury-based preservative) from any vaccine required by law as a precaution. All vaccines currently recommended for children in the US (with the exception of certain types of flu shots) are now totally mercury-free.
Originally published in American Baby magazine, February 2005, Update 2009